The Hubble Space Telescope has again captured Borisov's comet as it approaches the Sun. Prior to that, he managed to photograph this interstellar object in October and November this year. Pictures are published on the Hubble project website.
Comet 2I / Borisov was discovered on August 30, 2019 by Gennady Borisov, an employee of the astronomical station of the Moscow State University GAISh in Crimea. He announced his discovery to the Minor Planet Center of the International Astronomical Union in Cambridge (USA). The Center for the Study of Near-Earth Objects at NASA's Jet Propulsion Laboratory has calculated the comet's orbit, showing that it is an interstellar body that has come to us from another part of the galaxy.
2I / Borisov is only the second known interstellar object to fly through the solar system. The first was asteroid 1I / Oumuamua, which in October 2017 passed about 38 million kilometers from the Sun and left the solar system.
On October 12 this year, the Hubble Space Telescope managed to take a series of images of Borisov's comet flying at a speed of more than 175 thousand kilometers per hour at a distance of about 420 million kilometers from Earth.
On November 16, Hubble took another shot of the comet when it was 326 million kilometers from Earth. In this spectacular image, the comet is visible next to the spiral galaxy 2MASX J10500165-0152029. The galaxy's bright central core is blurred in the image because Hubble was tracking a comet. The tail of the ejected dust goes to the upper right corner.
And finally, on December 9, Hubble again captured the comet 2I / Borisov, now at the point of perihelion - during its closest approach to the Sun. At that moment, she was at a distance of 298 million kilometers from Earth, near the inner edge of the asteroid belt. Although this is the closest shot of the object, it is still impossible to clearly distinguish the nucleus, consisting of an accumulation of ice and dust, in the image, but the bright central part is clearly visible - a coma consisting of dust leaving the surface of the comet.
“Based on the images of the Hubble telescope, we can estimate the upper limit of the size of the nucleus of comet Borisov, which is very important,” David Jewitt, professor of planetary science and astronomy at the University of California, Los Angeles, quoted on the project website. but the images show that the nucleus has a radius of less than half a kilometer. This is about 15 times less than previous studies suggested. Knowing the size of the nucleus is useful for assessing how common such objects are in the solar system and in our galaxy. Borisov is the first known interstellar comet. and we would like to know how many more there might be."
According to scientists' calculations, Borisov's comet will approach the Earth as close as possible on December 28, when it will be at a distance of 290 million kilometers from us.